Second part
Already at altitudes of about 2900 m, according to some studies, 57% of people have at least one symptom of altitude sickness; of these, 6% are unable to continue the excursion. At the altitude of Capanna Margherita (4559 m), 30% of people have to reduce their activity or stay in bed, and 49% still suffer from milder symptoms. The most dangerous consequence is represented by cerebral edema (HACE).
The main cause of altitude sickness is the decrease in oxygen in the blood or hypoxemia, which causes an increase in the permeability of the capillaries with consequent leakage of fluids (edema) in the lungs and brain.
Pulmonary edema (HAPE) is due to the passage of water in the alveoli which normally contain air; causes severe respiratory insufficiency. It manifests itself with difficulty in breathing and tachycardia, initially dry cough and subsequently with pink and foamy spit, noisy breathing (rattle) , chest tightness and severe prostration. High-altitude pulmonary edema is found more frequently in young people, especially males.
The altitude at which pulmonary edema occurs appears to vary from place to place. For example, in the Peruvian Andes almost all cases occur after ascents to 12,000 feet (3,600 meters) and above, in the Himalayas to 11,000 feet (3,300 meters). ); cases of pulmonary edema have been reported in the United States after ascents to only 8,000-9,000 feet (2,400-2,700 meters).
Pulmonary Edema (HAPE): Frequency
Less than 0.2% for trekking or ascents in the Alpine area
4% of people affected by trekking in Nepal at altitudes above 4200
Pulmonary Edema (HAPE): Symptoms
At least 2 of: - Shortness of breath (dyspnoea) at rest - Dry cough - Tiredness - Decreased capacity - Chest tightness or congestion
Pulmonary Edema (HAPE): Signs
Increasing wheezing or rales on the lungs
Cyanosis
Rapid, labored breathing
Tachycardia
Pulmonary Edema (HAPE): Prevention
- Slow and gradual ascent, and, if possible, without using means of transport at high altitude
Acclimatization at high altitude
Nifedipine (ADALAT) 20 mg x 3 per day (starting 24 hours before the hike)
Dexamethasone
HAPE therapy
Oxygen
Nifedipine and possibly Dexametazone
Descent - Evacuation of the patient
In cerebral edema (swelling of the brain) there is a headache resistant to analgesics, vomiting, difficulty walking, progressive numbness up to a coma.
Severe altitude sickness occurs after milder symptoms, or suddenly.
Symptoms
- Severe respiratory disorders up to fatal acute pulmonary edema, ie the passage of blood in the pulmonary alveoli; edema is caused by pulmonary hypertension and by the increased permeability of the alveolar-capillary membrane. First persistent dry cough appears in succession, then, after a few hours, bloody foam in the mouth, great difficulty in breathing and a sense of suffocation; death intervenes within approximately 6 hours if no action is taken properly.
- Cerebral edema with severe pain-resistant headache, dizziness, jet vomiting, mental confusion, space-temporal disorientation, hallucinations, apathy, fainting, slow pulse and arterial hypertension. The skull is rigid and the swelling of the brain compresses the nerve centers causing the disorders described up to coma, that is, the complete loss of consciousness followed by death if not properly intervened.
Altitude sickness prevention
It would be advisable for every mountain visitor to periodically undergo screening tests, among which we recommend:
• Medical examination
• Basic laboratory tests. • Exercise ECG
• Spirometry
- Slow and gradual ascent, and, if possible, without using means of transport at high altitude
- Acclimatization at high altitude
- Acetazolamide (DIAMOX) 250 mg x 2 per day (starting 24 hours before the excursion)
Barometric pressure and IOP2 at different heights can be schematized as follows:
High altitude training
The altitude of interest, due to the physiological modifications, is that which is between 2500 and 4500 m as the highest point (Rifugio Capanna Regina Margherita, Monte Rosa, side of Alagna Valsesia). It was already known at the end of the 19th century that these heights already entailed problems for their visitors (who, for the mere fact of walking there, carried out high intensity physical and sporting activities) was already known at the end of the 19th century, so much so as to engage the mind and heart of one of the greats of the physiology, the Italian Angelo Mosso. It was precisely this passion that led him to create a real observation and research laboratory, in the first decade of the 1900s, at Col d "Olen (3000 m, right at the base of the final stretch that allows you to reach the 4500 m of the Capanna Margherita sul Rosa).
Today the mentioned altitude is considered as medium-high, according to a sum of observations of a climatic, meteorological, barometric and, obviously, altimetric order.
Altitude can be defined according to various criteria; the most interesting classification takes into account biological and physiological factors, distinguishing 4 distinct altitude levels on the basis of the modifications induced in the human organism. These limits should not be considered rigidly, as other factors can modulate the organism's response to hypoxia (subjective response, latitude, cold, air humidity, etc.).
At low altitudes (up to 1800 m) the pressure of the atmosphere varies from 760 mm Hg to 611 mm Hg. The partial pressure of oxygen (PpO2) ranges from 159 mm Hg to 128 mm Hg. The temperature should decrease by about 11 ° C, is actually influenced by various factors (rain, snow, vegetation etc.) which make it very variable Physiological adaptations are practically absent up to 1200 m asl, since the decrease in PpO2 and arterial oxygen saturation are minimal; VO2max (maximum aerobic power) according to some authors does not show significant changes, according to others there is already a slight reduction; in any case, all sports activities can be carried out without particular negative effects.
Up to about 3000 meters the atmospheric pressure varies from 611 mm Hg to 526 mm Hg. The PpO2 ranges from 128 mm Hg to 110 mm Hg. Here, too, the temperature is influenced by many environmental factors, but generally at 3000 m it reaches 5 degrees below zero. Acute exposure to these altitudes causes modest hyperventilation, increased heart rate (transient tachycardia), reduced stroke volume and increased hematocrit (increase in the number of red blood cells in relation to the liquid part of the blood). After a certain period of time the heart rate tends to drop to lower values, but it always remains higher than at sea level, while the systolic range is further reduced. Furthermore, with the permanence at altitudes above 2000 m, the viscosity of the blood increases. It is therefore reasonable to assume that exposure to these altitudes does not cause significant differences in the organism compared to those found at sea level. At these altitudes, the increase in blood viscosity seems to be due more to a reduction in the content of fluids in the body (which causes a relative increase in hematocrit), rather than a true increase in the production of red blood cells. Normally, during physical exercise there is a loss of fluids, which further increases at altitude and could be one of the causes of Hypoxic Syndrome and Altitude Sickness, which can also arise at medium altitude. verifies a reduction in VO2max directly proportional to the increase in altitude, which negatively affects endurance sports. While speed and power sports (jumps and throws) are favored by the lower force of gravity and lower air density.
From 3000 to 5500 m the atmospheric pressure varies from 526 mm Hg to 379 mm Hg. The PpO2 ranges from 110 mm Hg to 79 mm Hg. The temperature reaches 21 degrees below zero. At these altitudes physical activities undergo important limitations as the hypoxic stimulus becomes massive and the adaptation mechanisms create evident changes in the physiological and metabolic structure. For this reason, physical activity cannot be tolerated for a long time without adequate acclimatization and of training.
Prolonged stays above 3000 m of altitude often lead to a loss of weight and fluids due to the increased energy requirements and the particular environmental conditions. An adequate increase in the caloric (especially protein) and hydrosaline intake is therefore essential. The specific pathophysiology of these shares includes: damage from cold, acute and chronic mountain sickness, pulmonary edema and cerebral edema from high altitudes. Over 5500 m of altitude there are perennial snows at any latitude, temperatures reach 42 ° C below zero. In these environments the physiological adaptations do not allow a prolonged stay. Between 7500 and 9000 m the VO2max can be reduced by 30-40% and serious pathologies can easily affect anyone who stays at these altitudes, even if well acclimatized; the only possible precaution is to minimize the length of stay.
low altitude
average altitude
high altitude
altiss. quote
Altitude m
0 ÷ 1800
1800 ÷ 3000
3000 ÷ 5500
5500 ÷ 9000
Atmospheric pressure mmHg
760 ÷ 611
611 ÷ 525
525 ÷ 379
379 ÷ 231
Theoretical average temperature ° C
+15 ÷ +5
+4 ÷ -4
-5 ÷ -20
-21 ÷ -43
Alps vegetation
varies
coniferous-lich.
lichens
--
Andes vegetation
forest equ.
deciduous trees
conifers-lichens
--
Himalaya vegetation
trop forest.
deciduous trees
deciduous-lichens
--
Hemoglobin saturation%
> 95%
94% ÷ 91%
90% ÷ 81%
80% ÷ 62%
VO2max%
100 ÷ 96
95 ÷ 88
88 ÷ 61
60 ÷ 8
Symptomatology
absent
rare
frequent
very frequent
The "critical" factors of mountain training can be summarized as follows:
Physical and psychological effort required ("hostile environment")
Climatic factors
Experience, degree of training
Adequacy of the equipment
Age of the subject
Any individual pathologies (often not known or underestimated ...)
Knowledge of the itinerary
HYPOXIA
In recent years, many high-level athletes and athletic trainers have included training periods to be carried out at altitudes between 1800 and 2500 meters in various phases of the programming, often obtaining significant competitive results in endurance disciplines. However, the physiological-scientific data appear not to be univocal, resulting in a frequent discrepancy between favorable field experiences and scientific research.
Other articles on "Altura and altitude sickness"
- Altitude and training
- Training in the mountains
- Erythropoietin and altitude training
- Altitude training
- Altitude and alliance
